Solve for $n$: $5^{2n + 1} = \frac{1}{25}$. Express your answer as a common fraction.
Explanation: $\frac{1}{25}$ is equal to $5^{-2}$, so we have $5^{2n+1}=5^{-2}$.  This gives us $2n+1=-2$.  Solving for $n$ gives us $n=\boxed{-\frac{3}{2}}$.